Method and apparatus for assessing the play in bearings or joints of components coupled to one another

ABSTRACT

A method and an apparatus for assessing the play in bearings or joints of components coupled to one another, in particular wheel suspension or steering components of a motor vehicle. A simple automatic detection of the play is performed by providing that the components are subjected to alternating forces, and their positions at various times and/or their motions are detected optically, directly or indirectly, and from the detected position and/or motion data, a statement about the play is derived.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a 35 U.S.C. 371 application of PCT/DE 00/03588,Filed on Oct. 12, 2000.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a method and an apparatus for assessing theplay in bearings of joints of components coupled to one another, inparticular wheel suspension or steering components of a motor vehicle,in which the components are subjected to alternating forces.

2. Description of the Prior Art

Such a method and an apparatus intended for it is provided for instancein a test apparatus for primary examination of the technical status ofmotor vehicles. To monitor the bearing plays and joint plays in thecomponents of the wheel suspension and the steering, the wheels to betested are driven on a platform that is usually pneumatically actuated.By means of this platform, by manual tripping of the pneumatics, a forceis exerted via the tires on a vehicle wheel transversely to the traveldirection.

Because of the existing bearing and joint plays, displacements occuramong the components, which are observed visually. The tester then makesa subjective assessment of good or bad, based on his own experience, andat the same time this assessment forms the basis for deciding whethermaintenance work has to be done.

It is furthermore known, for measuring individual plays in bearings andjoints, to use known methods of length-measuring technology, such asmeters or gauges. The components are displaced counter to one another bythe exertion of defined forces in alternating force directions. Oneproblem of these methods is mounting measuring elements on thecomponents that have play, which makes these measuring methods difficultto employ in practice.

It is the object of the invention to furnish a method and an apparatusof the type referred to at the outset with which the assessment of theplay in bearings and joints can be done simply and automatically.

SUMMARY OF THE INVENTION

In the method, it is provided that the positions of the components atvarious times and/or their motions are ascertained optically eitherdirectly or indirectly (on the basis of further parts connected tothem), and from the position and/or motion data, a statement about theplay is derived. In the apparatus, it is provided that at the twocomponents coupled to one another, optically detectable features aredisposed or present directly or on further components in communicationwith them; and that an optical measuring instrument with apicture-taking system for detecting the features during their motion andwith an evaluation device for ascertaining the play from the position ofthe components or from their motion is provided. In this way, thelocations of the components and their motion are determined objectively,and from the measurement data, for instance on the basis of the variousposition patterns of the components at various times or from the motionpatterns, the play is ascertained. In the evaluation, the initiatedforces and their changes can also be taken into account. In this way,unambiguous statements regarding the play and an objective good/badassessment are obtained.

The method can be performed for instance at a testing site that is alsoused to determine the wheel and axle geometry, as described for instancein German Patent Disclosures DE 197 57 763 A1 and DE 197 57 760 A1, butthe introduction of the alternating forces must be done, and the motionof the coupled components or their position images must be taken intoaccount in the evaluation. By measuring the wheel motion relative to thevehicle body, or by measuring the change in wheel position (axlegeometry), a measurement of the total plays of the wheel suspensioncomponents or the steering components is possible.

One suitable procedure for this purpose is that simultaneously, imagedata from either a reference feature arrangement and a wheel or areference feature arrangement and at least one part of a vehicle body orof the wheel and at least one part of the body, or all three objects aredetected in such quick succession that the motions of the body and/orthe wheel are resolved; that the motion of the wheel and/or the body isdetermined from the image data; and that the play is determined as atotal play from a measurement of a wheel motion relative to the body orby measurement of the change in wheel position.

For further improvement in the accuracy of the play measurement, it isadvantageous if the wheels of one axle are measured chronologicallysynchronously.

The measurement of the play can be performed simply, for instance byproviding that the optical detection and the introduction of thealternating forces are effected during vehicle travel. The change inmotion can be effected here by braking and acceleration actions or turnsof the steering wheel to the right and left or by a suitable design ofthe roadway or by external excitations of the wheels.

Alternatively, the measurement or assessment of the play can be done insuch a way that the optical detection and introduction of thealternating forces are effected with the vehicle at a stop; to generatethe forces, turns of the steering wheel in opposite directions areperformed, or a force-introducing device known per se is used.

As the force-introducing device, in a primary examination, apneumatically actuated platform is for instance usual as a surface forthe wheels to stand on.

To improve the assessment of the steering play, it is also anadvantageous provision that to ascertain the steering play at the wheel,in addition the steering angle at the steering wheel is detectedelectronically or optically with a device known per se and is includedin the evaluation.

With the provisions recited, objective measurement values are obtained,as a result of which the necessity for performing repairs can also beassessed objectively and imparted to the vehicle owner.

The method and the apparatus make a one-dimensional (for instance, axialplay), two-dimensional (for instance, bearings out of true, radial play)or a three-dimensional play measurement possible within one measuringoperation, while in a subjective visual assessment essentially only asingle-dimensional detection of play is possible.

The method makes it possible to measure the effects of the existingbearing or joint plays on the vehicle wheel or the wheel position thatoccur under normal conditions of vehicle use (during vehicle travel) orunder special test conditions (for instance by introducing definedforces using a pneumatically actuated platform). Thus the influences ofbearing and joint plays in a specific vehicle that are relevant to wheelwear and driving safety are detected by measurement technology.

If the play measurement is performed in conjunction with another opticaltesting method using an optical picture-taking system, in particularcameras, for instance an optical axle measurement, then the apparatuscan be used in multiple ways, making the additional expense slight.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described below in terms of an exemplaryembodiment, in conjunction with the single drawing FIGURE which shows atesting site incorporating the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The testing site includes an apparatus 1 for assessing the play ofbearings or joints of wheel suspension or steering components of a motorvehicle. On a testing site floor 5, the apparatus 1 has a referencefeature arrangement 6 and picture-taking systems 2, installed on thesides, with picture-taking devices 2.1, in particular cameras. The motorvehicle is provided with vehicle body features 4 on its body in thevicinity of the wheels and with wheel features 3 on the wheels.

With the picture-taking system 2, which is in communication with anevaluation device or itself has an evaluation device, it is possible inrapid image order, by evaluation of the location of the wheel featuresand the vehicle body features, to ascertain the various wheel positionsand body positions or the motions of at least one wheel or of the body,and from the obtained location or motion data, under the influence ofalternating forces, which are generated for instance by accelerations orbraking operations or turns of the steering wheel in differentdirections during vehicle travel or by suitable design of the roadway orby external excitations of the wheel, to be measured. The alternatingforces themselves can be included in the evaluation. It is also possiblefor the motions of both wheels of one axle, for instance, to be detectedchronologically synchronously and compared with one another to improvethe outcomes of measurement.

The use of this apparatus 1 with the picture-taking system 2 fordetermining the play between the components during vehicle travel makesit possible summarily to detect all the bearing and joint plays underthe influence of the alternating forces as a consequence of the changesin motion. Because of the existing bearing and joint plays, changes inthe wheel geometry occur, which are detected by measurement technologywith the apparatus 1. With the chronologically synchronous measurementof the wheels of one axle, differences between the right and left wheelof the axle can be detected under identical operating conditions andtaken into account in the assessment.

In ascertaining the steering play at the wheel, an additionalimprovement in accuracy is possible because in addition the steeringangle is detected electronically, for instance with already knowndevices, and included in the evaluation. Alternatively, the detection ofthe steering angle at the steering wheel can also be done optically withan additional camera.

For exerting the alternating forces in the measurement of the totalplay, a known force-introducing device (for instance, a pneumaticallyactuated platform on which the vehicle stands) can be used. Then thechange in wheel position that occurs as a consequence of the alternatingload is detected. Advantageously, the wheels of one axle can beevaluated synchronously under identical load conditions.

A further variant of the method comprises measuring the play inindividual bearings or joints. To that end, the pairs of components tobe tested are marked, prior to the measurement, for instance by placingsuitable measuring marks on the components, in order to detect theirrelative motion under the influence of alternating load optically andevaluate it by measurement technology. Instead of special measuringmarks, simple colored markings can be used, or characteristic componentfeatures that are detectable by known methods of image processing can beevaluated.

A plurality of bearings and joints can be measured simultaneously, ifthey are within viewing range of the at least one camera. Here as well,the alternating load can be brought about by means of special testingconditions (such as a turn of the steering wheel, or platform motion).

The measurement can also be done in stationary machines, for example,under the alternating loads that occur in normal conditions of use.

If the play in the bearing or joint occurs in only one plane of motion,then it suffices to use only one camera for the optical measurement.Here as well it is possible to measure a plurality of bearings andjoints simultaneously, if they are detected as images by a camera andtheir planes of motion are either parallel to one another, or theirangular position relative to one another is known to the measurementsystem.

For detecting multiple degrees of freedom of the play for instancelinear (axial play), in a plane (bearing play) or rotationally (steeringwheel play)—an observation of the paired components to be tested, orparts coupled to them, is made from different perspectives, by means oftwo cameras, for instance. For simple automatic ascertainment of thepositioning of the cameras in each case, a reference feature arrangement6 known to the picture-taking system can be provided on the testingsite, as described in the references referred to at the outset, DE 19757 763 A1 and DE 197 57 760 A1. With a calibrated reference featurearrangement 6, it is simultaneously possible in a simple way to obtainabsolute measurement data. For deriving absolute measured values,factory calibration of the picture-taking system then becomesunnecessary.

The foregoing relates to preferred exemplary embodiments of theinvention, it being understood that other variants and embodimentsthereof are possible within the spirit and scope of the invention, thelatter being defined by the appended claims.

What is claimed is:
 1. A method for assessing the play in bearings orjoints of components coupled to one another, in which the components aresubjected to alternating forces, and a statement about the play isderived from an optical detection during the motion of the components,the method comprising: detecting the positions of the components atvarious times and/or their motions directly or indirectly as images bymeans of at least one camera, and evaluating the image data and derivinga statement about the play from the detected position and/or motiondata.
 2. The method of claim 1 wherein the components are wheelsuspension or steering components of a vehicle; and wherein the methodfurther comprises simultaneously obtaining image data from either areference feature arrangement and a wheel, or a reference featurearrangement and at least one part of a vehicle body, or of the wheel andat least one part of the body, or detecting all three objects in suchquick succession that the motions of the body and/or the wheel areresolved; determining the motion of the wheel and/or the body from theimage data; and determining the play as a total play from a measurementof a wheel motion relative to the body or by measurement of the changein wheel position.
 3. The method of claim 2, wherein the wheels of oneaxle are measured chronologically synchronously.
 4. The method of claim3 wherein the optical detection and the introduction of the alternatingforces are effected during vehicle travel.
 5. The method of claim 3wherein the optical detection and introduction of the alternating forcesare effected while the vehicle is stationary stopped, and to generatethe forces, either turns of the steering wheel in opposite directionsare performed, or a separate force-introducing device is used.
 6. Themethod of claim 2 wherein the optical detection and the introduction ofthe alternating forces are effected during vehicle travel.
 7. The methodof claim 6, wherein the introduction of the alternating forces iseffected by accelerations and braking operations or turns of thesteering wheel in opposite directions, or by suitable design of theroadway, or by external excitations of the wheels.
 8. The method ofclaim 2 wherein the optical detection and introduction of thealternating forces are effected while the vehicle is stationary, and togenerate the forces, either turns of the steering wheel in oppositedirections are performed, or a separate force-introducing device isused.
 9. The method of claim 2 wherein to ascertain the steering play atthe wheel, the steering angle at the steering wheel is detectedelectronically or optically and that information is included in theevaluation.
 10. The method of claim 1 wherein the optical detection andthe introduction of the alternating forces are effected during vehicletravel.
 11. The method of claim 10, wherein the introduction of thealternating forces is effected by accelerations and braking operationsor turns of the steering wheel in opposite directions, or by suitabledesign of the roadway, or by external excitations of the wheels.
 12. Themethod of claim 11 wherein to ascertain the steering play at the wheel,the steering angle at the steering wheel is detected electronically oroptically and that information is included in the evaluation.
 13. Themethod of claim 1 wherein the optical detection and introduction of thealternating forces are effected while the vehicle is stationary, and togenerate the forces, either turns of the steering wheel in oppositedirections are performed, or a separate force-introducing device isused.
 14. The method of claim 13 wherein to ascertain the steering playat the wheel, the steering angle at the steering wheel is detectedelectronically or optically and that information is included in theevaluation.
 15. The method of claim 1 wherein to ascertain the steeringplay at the wheel, the steering angle at the steering wheel is detectedelectronically or optically and that information is included in theevaluation.
 16. The method of claim 1 wherein for measuring play inindividual bearings or joints, the components to be tested are providedwith a measuring marking prior to the optical measurement, or componentfeatures that are already present on the components are detected; andthat the relative motion or position of the components to one another isascertained.
 17. An apparatus for assessing the play of bearings orjoints of components which are coupled to one another, comprising:optically detectable features (3, 4) on the components which are coupledto one another, or on further components in communication with them; andan optical measuring instrument with a picture-taking system (2) fordetecting the features during their motion and with an evaluation devicefor ascertaining the play of the components with respect to each otherfrom the position of the components or from their motion.
 18. Theapparatus of claim 17, wherein the components are wheel suspension orsteering components of a vehicle; the picture-taking system (2) isarranged for detecting wheel features (3) of at least one wheel andvehicle body features (4) of at least one adjacent part of the vehiclebody (4) during vehicle travel, or that the picture-taking system isarranged to detect the wheel features (3) of at least one wheel andvehicle body features (4) of at least one adjacent part of the vehiclebody, or features placed on the components.
 19. The apparatus of claim18 wherein the apparatus further comprising means, for additionallydetecting a steering angle.
 20. The apparatus of claim 18 wherein theapparatus further comprising a force-introducing device for subjectingat least one of the components directly or indirectly to alternatingforces.
 21. The apparatus of claim 18 wherein the apparatus furthercomprises a stationary reference feature (6) the stationary referencefeature (6) being included in the derivation of measurement data. 22.The apparatus of claim 17 wherein the apparatus further comprisingmeans, for additionally detecting a steering angle.
 23. The apparatus ofclaim 22 wherein the apparatus further comprising a force-introducingdevice for subjecting at least one of the components directly orindirectly to alternating forces.
 24. The apparatus of claim 22 whereinthe apparatus further comprises a stationary reference feature (6) thestationary reference feature (6) being included in the derivation ofmeasurement data.
 25. The apparatus of claim 17 wherein the apparatusfurther comprising a force-introducing device for subjecting at leastone of the components directly or indirectly to alternating forces. 26.The apparatus of claim 25 wherein the apparatus further comprises astationary reference feature (6) the stationary reference feature (6)being included in the derivation of measurement data.
 27. The apparatusof claim 17 wherein the apparatus further comprises a stationaryreference feature (6) the stationary reference feature (6) beingincluded in the derivation of measurement data.
 28. A method forassessing the play in bearings or joints of components, which play isgenerated by subjecting the components to alternating forces, andgenerating a statement about the play during the motion of thecomponents, the method comprising the steps of: detecting the positionsof the components at various times and/or their motions directly orindirectly as images by means of at least one camera, subjecting thecomponents to alternating forces during the detecting step, andevaluating the image data and deriving a statement about the play fromthe information gathered during the detecting step.
 29. An apparatus forassessing the play of bearings or joints of components which are coupledto one another, comprising: optically detectable features (3, 4) on thecomponents which are coupled to one another, or on further components incommunication with them; an optical measuring instrument for detectingthe features and their relative positions during their motion; and anevaluation device for ascertaining the play of the components withrespect to each other from the relative positions of the features of thecomponents, or from the relative motion of the features of thecomponents.